Applies to SUSE Linux Enterprise Server 15 SP3

20 Printer operation #

SUSE® Linux Enterprise Server supports printing with many types of printers, including remote network printers. Printers can be configured manually or with YaST. For configuration instructions, refer to Sección 20.3, “Configuración de una impresora”. Both graphical and command line utilities are available for starting and managing print jobs. If your printer does not work as expected, refer to Section 20.8, “Troubleshooting”.

CUPS (Common Unix Printing System) is the standard print system in SUSE Linux Enterprise Server.

Printers can be distinguished by interface, such as USB or network, and printer language. When buying a printer, make sure that the printer has an interface that is supported (USB, Ethernet, or Wi-Fi) and a suitable printer language. Printers can be categorized on the basis of the following three classes of printer languages:

PostScript printers

PostScript is the printer language in which most print jobs in Linux and Unix are generated and processed by the internal print system. If PostScript documents can be processed directly by the printer and do not need to be converted in additional stages in the print system, the number of potential error sources is reduced.

Currently PostScript is being replaced by PDF as the standard print job format. PostScript+PDF printers that can directly print PDF (in addition to PostScript) already exist. For traditional PostScript printers PDF needs to be converted to PostScript in the printing workflow.

Standard printers (languages like PCL and ESC/p)

In the case of known printer languages, the print system can convert PostScript jobs to the respective printer language with Ghostscript. This processing stage is called interpreting. The best-known languages are PCL (which is mostly used by HP printers and their clones) and ESC/P (which is used by Epson printers). These printer languages are usually supported by Linux and produce an adequate print result. Linux may not be able to address some special printer functions. Except for HP and Epson, there are currently no printer manufacturers who develop Linux drivers and make them available to Linux distributors under an open source license.

Proprietary printers (also called GDI printers)

These printers do not support any of the common printer languages. They use their own undocumented printer languages, which are subject to change when a new edition of a model is released. Usually only Windows drivers are available for these printers. See Section 20.8.1, “Printers without standard printer language support” for more information.

Before you buy a new printer, refer to the following sources to check how well the printer you intend to buy is supported:

http://www.openprinting.org/printers: The OpenPrinting home page with the printer database. The database shows the latest Linux support status. However, a Linux distribution can only integrate the drivers available at production time. Accordingly, a printer currently rated as “perfectly supported” may not have had this status when the latest SUSE Linux Enterprise Server version was released. Thus, the databases may not necessarily indicate the correct status, but only provide an approximation.
https://www.ghostscript.com: The Ghostscript Web page.
/usr/share/doc/packages/ghostscript/catalog.devices: List of built-in Ghostscript drivers.

20.1 The CUPS workflow #

The user creates a print job. The print job consists of the data to print plus information for the spooler. This includes the name of the printer or the name of the print queue, and optionally, information for the filter, such as printer-specific options.

At least one dedicated print queue exists for every printer. The spooler holds the print job in the queue until the desired printer is ready to receive data. When the printer is ready, the spooler sends the data through the filter and back-end to the printer.

The filter converts the data generated by the application that is printing (usually PostScript or PDF, but also ASCII, JPEG, etc.) into printer-specific data (PostScript, PCL, ESC/P, etc.). The features of the printer are described in the PPD files. A PPD file contains printer-specific options with the parameters needed to enable them on the printer. The filter system makes sure that options selected by the user are enabled.

If you use a PostScript printer, the filter system converts the data into printer-specific PostScript. This does not require a printer driver. If you use a non-PostScript printer, the filter system converts the data into printer-specific data. This requires a printer driver suitable for your printer. The back-end receives the printer-specific data from the filter then passes it to the printer.

20.2 Methods and protocols for connecting printers #

There are various possibilities for connecting a printer to the system. The configuration of CUPS does not distinguish between a local printer and a printer connected to the system over the network. For more information about the printer connection, read the article CUPS in a Nutshell at https://en.opensuse.org/SDB:CUPS_in_a_Nutshell.

IBM Z Printers and similar devices provided by the z/VM that connect locally with the IBM Z mainframes are not supported by CUPS. On these platforms, printing is only possible over the network. The cabling for network printers must be installed according to the instructions of the printer manufacturer.

Warning: Changing cable connections in a running system

When connecting the printer to the machine, do not forget that only USB devices can be plugged in or unplugged during operation. To avoid damaging your system or printer, shut down the system before changing any connections that are not USB.

20.3 Installing the software #

PPD (PostScript printer description) is the computer language that describes the properties, like resolution, and options, such as the availability of a duplex unit. These descriptions are required for using various printer options in CUPS. Without a PPD file, the print data would be forwarded to the printer in a “raw” state, which is usually not desired.

To configure a PostScript printer, the best approach is to get a suitable PPD file. Many PPD files are available in the packages manufacturer-PPDs and OpenPrintingPPDs-postscript. See Section 20.7.3, “PPD files in various packages” and Section 20.8.2, “No suitable PPD file available for a PostScript printer”.

New PPD files can be stored in the directory /usr/share/cups/model/ or added to the print system with YaST as described in Sección 20.3.1.1, “Adición de controladores con YaST”. Subsequently, the PPD file can be selected during the printer setup.

Be careful if a printer manufacturer wants you to install entire software packages. This kind of installation may result in the loss of the support provided by SUSE Linux Enterprise Server. Also, print commands may work differently and the system may no longer be able to address devices of other manufacturers. For this reason, the installation of manufacturer software is not recommended.

20.4 Network printers #

A network printer can support various protocols, some even concurrently. Although most of the supported protocols are standardized, some manufacturers modify the standard. Manufacturers then provide drivers for only a few operating systems. Unfortunately, Linux drivers are rarely provided. The current situation is such that you cannot act on the assumption that every protocol works smoothly in Linux. Therefore, you may need to experiment with various options to achieve a functional configuration.

CUPS supports the socket, LPD, IPP and smb protocols.

socket: Socket refers to a connection in which the plain print data is sent directly to a TCP socket. Some socket port numbers that are commonly used are 9100 or 35. The device URI (uniform resource identifier) syntax is: socket://IP.OF.THE.PRINTER:PORT, for example: socket://192.168.2.202:9100/.
LPD (line printer daemon): The LPD protocol is described in RFC 1179. Under this protocol, some job-related data, such as the ID of the print queue, is sent before the actual print data is sent. Therefore, a print queue must be specified when configuring the LPD protocol. The implementations of diverse printer manufacturers are flexible enough to accept any name as the print queue. If necessary, the printer manual should indicate what name to use. LPT, LPT1, LP1 or similar names are often used. The port number for an LPD service is 515. An example device URI is lpd://192.168.2.202/LPT1.
IPP (Internet printing protocol): IPP is based on the HTTP protocol. With IPP, more job-related data is transmitted than with the other protocols. CUPS uses IPP for internal data transmission. The name of the print queue is necessary to configure IPP correctly. The port number for IPP is 631. Example device URIs are ipp://192.168.2.202/ps and ipp://192.168.2.202/printers/ps.
SMB (Windows share): CUPS also supports printing on printers connected to Windows shares. The protocol used for this purpose is SMB. SMB uses the port numbers 137, 138 and 139. Example device URIs are smb://user:password@workgroup/smb.example.com/printer, smb://user:password@smb.example.com/printer, and smb://smb.example.com/printer.

The protocol supported by the printer must be determined before configuration. If the manufacturer does not provide the needed information, the command nmap (which comes with the nmap package) can be used to ascertain the protocol. nmap checks a host for open ports. For example:

> nmap -p 35,137-139,515,631,9100-10000 IP.OF.THE.PRINTER

20.5 Configuring CUPS with command line tools #

CUPS can be configured with command line tools like lpinfo, lpadmin and lpoptions. You need a device URI consisting of a back-end, such as USB, and parameters. To determine valid device URIs on your system use the command lpinfo -v | grep ":/":

> sudo lpinfo -v | grep ":/"
direct usb://ACME/FunPrinter%20XL
network socket://192.168.2.253

With lpadmin the CUPS server administrator can add, remove or manage print queues. To add a print queue, use the following syntax:

> sudo lpadmin -p QUEUE -v DEVICE-URI -P PPD-FILE -E

Then the device (-v) is available as QUEUE (-p), using the specified PPD file (-P). This means that you must know the PPD file and the device URI to configure the printer manually.

Do not use -E as the first option. For all CUPS commands, -E as the first argument sets use of an encrypted connection. To enable the printer, -E must be used as shown in the following example:

> sudo lpadmin -p ps -v usb://ACME/FunPrinter%20XL -P \
/usr/share/cups/model/Postscript.ppd.gz -E

The following example configures a network printer:

> sudo lpadmin -p ps -v socket://192.168.2.202:9100/ -P \
/usr/share/cups/model/Postscript-level1.ppd.gz -E

For more options of lpadmin, see the man page of lpadmin(8).

During printer setup, certain options are set as default. These options can be modified for every print job (depending on the print tool used). Changing these default options with YaST is also possible. Using command line tools, set default options as follows:

First, list all options:
```
> sudo lpoptions -p QUEUE -l
```
Example:
```
Resolution/Output Resolution: 150dpi *300dpi 600dpi
```
The activated default option is identified by a preceding asterisk (*).

Change the option with lpadmin:

> sudo lpadmin -p QUEUE -o Resolution=600dpi

Check the new setting:

> sudo lpoptions -p QUEUE -l

Resolution/Output Resolution: 150dpi 300dpi *600dpi

When a normal user runs lpoptions, the settings are written to ~/.cups/lpoptions. However, root settings are written to /etc/cups/lpoptions.

20.6 Printing from the command line #

To print from the command line, enter lp -d QUEUENAME FILENAME, substituting the corresponding names for QUEUENAME and FILENAME.

Some applications rely on the lp command for printing. In this case, enter the correct command in the application's print dialog, usually without specifying FILENAME, for example, lp -d QUEUENAME.

20.7 Special features in SUSE Linux Enterprise Server #

Several CUPS features have been adapted for SUSE Linux Enterprise Server. Some of the most important changes are covered here.

20.7.1 CUPS and firewall #

After completing a default installation of SUSE Linux Enterprise Server, firewalld is active and the network interfaces are configured to be in the public zone, which blocks incoming traffic.

When firewalld is active, you may need to configure it to allow clients to browse network printers by allowing mdns and ipp through the internal network zone. The public zone should never expose printer queues.

(More information about the firewalld configuration is available in Section 23.4, “firewalld” and at https://en.opensuse.org/SDB:CUPS_and_SANE_Firewall_settings.)

20.7.1.1 CUPS client #

Normally, a CUPS client runs on a regular workstation located in a trusted network environment behind a firewall. In this case it is recommended to configure the network interface to be in the Internal Zone, so the workstation is reachable from within the network.

20.7.1.2 CUPS server #

If the CUPS server is part of a trusted network environment protected by a firewall, the network interface should be configured to be in the Internal Zone of the firewall. It is not recommended to set up a CUPS server in an untrusted network environment unless you ensure that it is protected by special firewall rules and secure settings in the CUPS configuration.

20.7.2 Browsing for network printers #

CUPS servers regularly announce the availability and status information of shared printers over the network. Clients can access this information to display a list of available printers in printing dialogs, for example. This is called “browsing”.

CUPS servers announce their print queues over the network either via the traditional CUPS browsing protocol, or via Bonjour/DNS-SD. To enable browsing network print queues, the service cups-browsed needs to run on all clients that print via CUPS servers. cups-browsed is not started by default. To start it for the active session, use sudo systemctl start cups-browsed. To ensure it is automatically started after booting, enable it with sudo systemctl enable cups-browsed on all clients.

In case browsing does not work after having started cups-browsed, the CUPS server(s) probably announce the network print queues via Bonjour/DNS-SD. In this case you need to additionally install the package avahi and start the associated service with sudo systemctl start avahi-daemon on all clients.

See Section 20.7.1, “CUPS and firewall” for information on allowing printer browsing through firewalld.

20.7.3 PPD files in various packages #

The YaST printer configuration sets up the queues for CUPS using the PPD files installed in /usr/share/cups/model. To find the suitable PPD files for the printer model, YaST compares the vendor and model determined during hardware detection with the vendors and models in all PPD files. For this purpose, the YaST printer configuration generates a database from the vendor and model information extracted from the PPD files.

The configuration using only PPD files and no other information sources has the advantage that the PPD files in /usr/share/cups/model can be modified freely. For example, if you have PostScript printers the PPD files can be copied directly to /usr/share/cups/model (if they do not already exist in the manufacturer-PPDs or OpenPrintingPPDs-postscript packages) to achieve an optimum configuration for your printers.

Additional PPD files are provided by the following packages:

gutenprint: the Gutenprint driver and its matching PPDs
splix: the SpliX driver and its matching PPDs
OpenPrintingPPDs-ghostscript: PPDs for Ghostscript built-in drivers
OpenPrintingPPDs-hpijs: PPDs for the HPIJS driver for non-HP printers

20.8 Troubleshooting #

The following sections cover some of the most frequently encountered printer hardware and software problems and ways to solve or circumvent these problems. Among the topics covered are GDI printers, PPD files and port configuration. Common network printer problems, defective printouts, and queue handling are also addressed.

20.8.1 Printers without standard printer language support #

These printers do not support any common printer language and can only be addressed with special proprietary control sequences. Therefore they can only work with the operating system versions for which the manufacturer delivers a driver. GDI is a programming interface developed by Microsoft* for graphics devices. Usually the manufacturer delivers drivers only for Windows, and since the Windows driver uses the GDI interface these printers are also called GDI printers. The actual problem is not the programming interface, but that these printers can only be addressed with the proprietary printer language of the respective printer model.

Some GDI printers can be switched to operate either in GDI mode or in one of the standard printer languages. See the manual of the printer whether this is possible. Some models require special Windows software to do the switch (note that the Windows printer driver may always switch the printer back into GDI mode when printing from Windows). For other GDI printers there are extension modules for a standard printer language available.

Some manufacturers provide proprietary drivers for their printers. The disadvantage of proprietary printer drivers is that there is no guarantee that these work with the installed print system or that they are suitable for the various hardware platforms. In contrast, printers that support a standard printer language do not depend on a special print system version or a special hardware platform.

Instead of spending time trying to make a proprietary Linux driver work, it may be more cost-effective to purchase a printer which supports a standard printer language (preferably PostScript). This would solve the driver problem once and for all, eliminating the need to install and configure special driver software and obtain driver updates that may be required because of new developments in the print system.

20.8.2 No suitable PPD file available for a PostScript printer #

If the manufacturer-PPDs or OpenPrintingPPDs-postscript packages do not contain a suitable PPD file for a PostScript printer, it should be possible to use the PPD file from the driver CD of the printer manufacturer or download a suitable PPD file from the Web page of the printer manufacturer.

If the PPD file is provided as a zip archive (.zip) or a self-extracting zip archive (.exe), unpack it with unzip. First, review the license terms of the PPD file. Then use the cupstestppd utility to check if the PPD file complies with “Adobe PostScript Printer Description File Format Specification, version 4.3.” If the utility returns “FAIL,” the errors in the PPD files are serious and are likely to cause major problems. The problem spots reported by cupstestppd should be eliminated. If necessary, ask the printer manufacturer for a suitable PPD file.

20.8.3 Network printer connections #

Identifying network problems

Connect the printer directly to the computer. For test purposes, configure the printer as a local printer. If this works, the problems are related to the network.

Checking the TCP/IP network

The TCP/IP network and name resolution must be functional.

Checking a remote lpd

Use the following command to test if a TCP connection can be established to lpd (port 515) on HOST:

> netcat -z HOST 515 && echo ok || echo failed

If the connection to lpd cannot be established, lpd may not be active or there may be basic network problems.

Provided that the respective lpd is active and the host accepts queries, run the following command as root to query a status report for QUEUE on remote HOST:

# echo -e "\004queue" \
| netcat -w 2 -p 722 HOST 515

If lpd does not respond, it may not be active or there may be basic network problems. If lpd responds, the response should show why printing is not possible on the queue on host. If you receive a response like that shown in Example 20.1, “Error message from lpd”, the problem is caused by the remote lpd.

Example 20.1: Error message from lpd #

lpd: your host does not have line printer access
lpd: queue does not exist
printer: spooling disabled
printer: printing disabled

Checking a remote cupsd

A CUPS network server can broadcast its queues by default every 30 seconds on UDP port 631. Accordingly, the following command can be used to test whether there is a broadcasting CUPS network server in the network. Make sure to stop your local CUPS daemon before executing the command.

> netcat -u -l -p 631 & PID=$! ; sleep 40 ; kill $PID

If a broadcasting CUPS network server exists, the output appears as shown in Example 20.2, “Broadcast from the CUPS network server”.

Example 20.2: Broadcast from the CUPS network server #

ipp://192.168.2.202:631/printers/queue

IBM Z Take into account that IBM Z Ethernet devices do not receive broadcasts by default.

The following command can be used to test if a TCP connection can be established to cupsd (port 631) on HOST:

> netcat -z HOST 631 && echo ok || echo failed

If the connection to cupsd cannot be established, cupsd may not be active or there may be basic network problems. lpstat -h HOST -l -t returns a (possibly very long) status report for all queues on HOST, provided the respective cupsd is active and the host accepts queries.

The next command can be used to test if the QUEUE on HOST accepts a print job consisting of a single carriage-return character. Nothing should be printed. Possibly, a blank page may be ejected.

> echo -en "\r" \
| lp -d queue -h HOST

Troubleshooting a Network Printer or Print Server Machine

Spoolers running in a print server machine sometimes cause problems when they need to deal with multiple print jobs. Since this is caused by the spooler in the print server machine, there no way to resolve this issue. As a work-around, circumvent the spooler in the print server machine by addressing the printer connected to the print server machine directly with the TCP socket. See Section 20.4, “Network printers”.

In this way, the print server machine is reduced to a converter between the various forms of data transfer (TCP/IP network and local printer connection). To use this method, you need to know the TCP port on the print server machine. If the printer is connected to the print server machine and turned on, this TCP port can usually be determined with the nmap utility from the nmap package some time after the print server machine is powered up. For example, nmap IP-address may deliver the following output for a print server machine:

Port       State       Service
23/tcp     open        telnet
80/tcp     open        http
515/tcp    open        printer
631/tcp    open        cups
9100/tcp   open        jetdirect

This output indicates that the printer connected to the print server machine can be addressed via TCP socket on port 9100. By default, nmap only checks several commonly known ports listed in /usr/share/nmap/nmap-services. To check all possible ports, use the command nmap -p FROM_PORT-TO_PORT IP_ADDRESS. This may take some time. For further information, refer to the man page of nmap.

Enter a command like

> echo -en "\rHello\r\f" | netcat -w 1 IP-address port
cat file | netcat -w 1 IP-address port

to send character strings or files directly to the respective port to test if the printer can be addressed on this port.

20.8.4 Defective printouts without error message #

For the print system, the print job is completed when the CUPS back-end completes the data transfer to the recipient (printer). If further processing on the recipient fails (for example, if the printer is not able to print the printer-specific data) the print system does not notice this. If the printer cannot print the printer-specific data, select a PPD file that is more suitable for the printer.

20.8.5 Disabled queues #

If the data transfer to the recipient fails entirely after several attempts, the CUPS back-end, such as USB or socket, reports an error to the print system (to cupsd). The back-end determines how many unsuccessful attempts are appropriate until the data transfer is reported as impossible. As further attempts would be in vain, cupsd disables printing for the respective queue. After eliminating the cause of the problem, the system administrator must re-enable printing with the command cupsenable.

20.8.6 CUPS browsing: deleting print jobs #

If a CUPS network server broadcasts its queues to the client hosts via browsing and a suitable local cupsd is active on the client hosts, the client cupsd accepts print jobs from applications and forwards them to the cupsd on the server. When cupsd on the server accepts a print job, it is assigned a new job number. Therefore, the job number on the client host is different from the job number on the server. As a print job is usually forwarded immediately, it cannot be deleted with the job number on the client host This is because the client cupsd regards the print job as completed when it has been forwarded to the server cupsd.

To delete the print job on the server, use a command such as lpstat -h cups.example.com -o to determine the job number on the server. This assumes that the server has not already completed the print job (that is, sent it completely to the printer). Use the obtained job number to delete the print job on the server as follows:

> cancel -h cups.example.com QUEUE-JOBNUMBER

20.8.7 Defective print jobs and data transfer errors #

If you switch the printer off or shut down the computer during the printing process, print jobs remain in the queue. Printing resumes when the computer (or the printer) is switched back on. Defective print jobs must be removed from the queue with cancel.

If a print job is corrupted or an error occurs in the communication between the host and the printer, the printer cannot process the data correctly and prints numerous sheets of paper with unintelligible characters. To fix the problem, follow these steps:

To stop printing, remove all paper from ink jet printers or open the paper trays of laser printers. High-quality printers have a button for canceling the current printout.
The print job may still be in the queue, because jobs are only removed after they are sent completely to the printer. Use lpstat -o or lpstat -h cups.example.com -o to check which queue is currently printing. Delete the print job with cancel QUEUE-JOBNUMBER or cancel -h cups.example.com QUEUE-JOBNUMBER.
Some data may still be transferred to the printer even though the print job has been deleted from the queue. Check if a CUPS back-end process is still running for the respective queue and terminate it.
Reset the printer completely by switching it off for some time. Then insert the paper and turn on the printer.

20.8.8 Debugging CUPS #

Use the following generic procedure to locate problems in CUPS:

Set LogLevel debug in /etc/cups/cupsd.conf.
Stop cupsd.
Remove /var/log/cups/error_log* to avoid having to search through very large log files.
Start cupsd.
Repeat the action that led to the problem.
Check the messages in /var/log/cups/error_log* to identify the cause of the problem.

20.8.9 More information #

In-depth information about printing on SUSE Linux Enterprise Server is presented in the openSUSE Support Database at https://en.opensuse.org/Portal:Printing. Solutions to many specific problems are presented in the SUSE Knowledgebase (https://www.suse.com/support/). Locate the relevant articles with a text search for CUPS.